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  <script>
    // 之前逻辑 弄个盒子 第三方 装
    // var leftApple = '青苹果'
    // var rightApple = '红苹果'

    // var box

    // box = leftApple  // 青苹果
    // leftApple = rightApple  // 红苹果
    // rightApple = box

    // console.log(rightApple)
    // console.log(leftApple)


    // 左手 5  右手 3， 不允许 第三个变量  逻辑思维了
    var leftNum = 5, rightNum = 3
      //    8            3
    leftNum = leftNum + rightNum  // 8

    rightNum = leftNum - rightNum  // 8 - 3  = 5

    leftNum = leftNum - rightNum  //8 - 5 = 3

    console.log(rightNum)  // 5
    console.log(leftNum)  // 3

  </script>
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